1. Field
The present invention relates to a semiconductor plastic package and a method of fabricating the semiconductor plastic package.
2. Description of the Related Art
Current electronic devices are trending towards smaller, thinner, and lighter products. In step with these trends, the preferred method for mounting a semiconductor chip is changing from the wire bonding method to the flip chip method, which allows a greater number of terminals. Accordingly, there is a demand also for higher reliability and higher densities in the multilayer printed circuit board to which the semiconductor chip may be mounted.
In the conventional multilayer printed circuit board, if glass fiber woven fabric is used for the base material, E-glass is generally used for the glass component. A thermosetting resin composition may be impregnated into the fiberglass woven fabric, dried, and put in a B-stage condition, which can then be processed into a copper clad laminate. This copper clad laminate can be used to fabricate a printed circuit board core, for use in the inner layers, over which B-stage resin sheets may be stacked on either side as build-up layers, to manufacture a multilayer printed circuit board.
A multilayer printed circuit board thus manufactured may include a build-up resin composition that has a high rate of thermal expansion (generally about 18 to 100 ppm/° C. in the longitudinal and lateral directions) and may include solder resists on the outermost surfaces that have an even higher rate of thermal expansion (generally about 50 to 150 ppm/° C.). Consequently, the overall coefficient of thermal expansion in the longitudinal and lateral directions for the multilayer printed circuit board may be about 13 to 30 ppm/° C. This coefficient of thermal expansion of the multilayer printed circuit board may be relatively higher than the coefficient of thermal expansion of the semiconductor chip, which generally ranges about 2 to 3 ppm/° C.
If there is a difference in the coefficients of thermal expansion between the semiconductor chip and the multilayer printed circuit board, mounting the semiconductor chip onto the multilayer printed circuit board can lead to the occurrence of defects, such as cracking in the connecting portions between the semiconductor chip and the board, and the semiconductor chip being delaminated or damaged. Also, if the semiconductor chip is placed on just one side of the board, the multilayer printed circuit board may be bent or warped.